This invention relates to the field of noninvasive surgery for the relief of atherosclerotic obstructions of arteries known as angioplasty or the internal remodeling of arteries in which there is physical displacement of the atherosclerotic material. Such noninvasive surgery comprises methods of repair of diseased or distorted internal bodily structures through the use of instruments placed via skin puncture rather than a large operative incision.
The invention contemplates a catheter adapted to be inserted in the blood vessel that may have a section of abnormal deposits such as atherosclerotic plaque, for the purpose of cutting away the deposits.
A number of current methods for removing such deposits exists that are designed to treat this problem of vessel obstruction. However significant problems and limitations apply to the prior art approaches.
A widely employed approach is percutaneous transluminal balloon angioplasty in which a large bore guiding catheter is placed in a peripheral artery and through this guiding catheter a balloon catheter is passed to the section of the artery to be treated and the balloon is inflated within the arterial narrowing or lesion. The purpose of this procedure is to disrupt or push aside atherosclerotic plaque material that is obstructing the vessel so that blood flow to the region fed by that vessel is improved. Disadvantages of the method include acute vessel closure or collapse requiring emergency coronary artery bypass surgery and also reappearance of the blockage. The procedure may also be accompanied by thrombus formation and dissection. Means for alleviating particularly long blockages have not been successful and also means of administering drug therapy directly to the affected site is limited. Refinements and modifications of this technique include atherectomy devices through which athersclorotic material is removed by shaving or milling and also the use of laser energy. In general the uses of these devices which are often more complex and expensive than conventional balloon catheters and often require adjunctive balloon catheter dilation has not improved the overall rate of restenosis. In addition the issues of how to avoid damage to normal healthy arterial wall and how to protect and remove detached atherosclerotic debris have required further attention.
An example of the prior art apparatus is shown in U.S. Pat. No. 4,445,509 to Auth which shows apparatus for the removal of deposits by means of a cutting tool secured at one end of a flexible rotating shaft adapted to be inserted into a blood vessel. An actuator rotates the cutting tool to remove the deposits from the vessel walls and thereafter the particles of deposit are dispersed in the bloodstream without actually being removed from the body.
In this type of apparatus the rotating tool is of fixed diameter and mills and opening in the occluded or plaque deposit section in accordance with the tool diameter. To open a section that is heavily deposited it is often necessary to use a first cutting tool of small diameter and then subsequent tools of progressively larger diameters.
This need for multiple tools of different diameters to open an occluded section is a particular disadvantage of such prior art devices.
A further disadvantage of devices of the prior art is that particles of plaque deposit pass into the blood stream after they are milled by the cutting tool.